This invention relates in general to the field of communications systems and, more specifically, to a magnetic antenna capable of collecting frequency emissions.
Magnetic antennae used, for example, by the intelligence community collect frequency emissions from xe2x80x9careas-of-interestxe2x80x9d including machinery and equipment used in underground and above ground facilities. Fabrication of conventional magnetic antennae is such that each winding in a three dimensional structure is wound around a different turns area. In an effort to create approximately equal turns-area ratios between the windings, conventional techniques typically require using a different number of turns in each winding. Attempting to match turns-area ratios by using unequal numbers of turns in the windings is difficult and inaccurate. Moreover, a change in the number of turns wound around a given turns area causes the impedance in each winding to differ. Counteracting this effect typically requires the placement of a resistive element in each winding. This overall process leads to increased expense and processing time and still does not ensure balanced induced fields within the magnetic antenna.
The present invention recognizes a need for an improved method and apparatus for collecting frequency emissions. In accordance with the present invention, a method and apparatus for collecting sub-high frequency radio emissions is provided that reduce or eliminate at least some of the shortcomings associated with prior approaches.
In one aspect of the invention, an antenna device operable to collect sub-high frequency radio signals comprises a three dimensional support structure. A first winding is disposed outwardly from the three dimensional support structure and wound around a first axis of the three dimensional support structure. The antenna further comprises a second winding disposed outwardly from the three dimensional support structure and the first winding and wound around a second axis orthogonal to the first axis of the three dimensional support structure. In one particular embodiment, the first winding and the second winding each comprise an approximately equal turns area.
In another aspect of the invention, a method of forming an antenna operable to collect sub-high frequency radio signals comprises forming a first winding disposed outwardly from a three dimensional support structure and wound around a first axis of the three dimensional support structure. The method further comprises forming a second winding disposed outwardly from the three dimensional support structure and the first winding and wound around a second axis orthogonal to the first axis of the three dimensional support structure. In one particular embodiment, the first winding and the second winding each comprise an approximately equal turns area.
Depending on the specific features implemented, particular embodiments of the present invention may exhibit some, none, or all of the following technical advantages. Various aspects of the invention create an approximately equal turns area in at least two of the plurality of substantially orthogonal windings, which enables the formation of approximately balanced induced fields in those windings using a substantially similar number of turns in each winding. Various embodiments of the present invention facilitate the creation of a filter shield with approximately equal inductance in each filter circuit.
Other technical advantages will be readily apparent to one skilled in the art from the following figures, descriptions and claims. Moreover, while specific advantages have been enumerated above, various embodiments may include all, some or none of the enumerated advantages.